As a young massive cluster in the Central Molecular Zone , the Arches cluster is a valuable probe of the stellar Initial Mass Function ( IMF ) in the extreme Galactic Center environment .
We use multi-epoch Hubble Space Telescope observations to obtain high-precision proper motion and photometric measurements of the cluster , calculating cluster membership probabilities for stars down to \sim 1.8 M _ { \odot } between cluster radii of 0.25 pc – 3.0 pc .
We achieve a cluster sample with just \sim 6 % field contamination , a significant improvement over photometrically-selected samples which are severely compromised by the differential extinction across the field .
Combining this sample with K-band spectroscopy of 5 cluster members , we forward model the Arches cluster to simultaneously constrain its IMF and other properties ( such as age and total mass ) while accounting for observational uncertainties , completeness , mass segregation , and stellar multiplicity .
We find that the Arches IMF is best described by a 1-segment power law that is significantly top-heavy : \alpha = 1.80 \pm 0.05 ( stat ) \pm 0.06 ( sys ) , where dN/dm \propto m ^ { - \alpha } , though we can not discount a 2-segment power law model with a high-mass slope only slightly shallower than local star forming regions ( \alpha = 2.04 ^ { +0.14 } _ { -0.19 } \pm 0.04 ) but with a break at 5.8 ^ { +3.2 } _ { -1.2 } \pm 0.02 M _ { \odot } .
In either case , the Arches IMF is significantly different than the standard IMF .
Comparing the Arches to other young massive clusters in the Milky Way , we find tentative evidence for a systematically top-heavy IMF at the Galactic Center .